Cards that have an IC module therein and are capable of non-contact data sending/receiving through an external reader or writer are spreading in recent years. IC labels for use in the same application have been proposed that have a pressure-sensitive adhesive layer and are used after having been bonded to an adherend (see, for example, patent documents 1, 2, and 3).
A label for in-mold forming is known as one mode of label. This label can be used to produce a labeled resin molding in the following manner. The label is set beforehand in a mold so as to be in contact with the mold wall. A molten thermoplastic resin is injection-molded with the mold, or a parison of a molten thermoplastic resin is introduced into the mold and blow-molded. Alternatively, a sheet of a molten thermoplastic resin is molded with the mold by vacuum forming or pressure forming. (See, for example, patent documents 4 and 5).
Compared to pressure-sensitive adhesive labels employing a pressure-sensitive adhesive, such labels for in-mold forming are advantageous because they attain high adhesion strength, have excellent water resistance and durability, and can retain stable adhesion strength even in a low-temperature environment having a temperature lower than the glass transition point of the pressure-sensitive adhesive. In addition, since labels for in-mold forming that have been bonded cannot be stripped off and applied again, the labels have an advantage that frauds such as disguise and alteration can be prevented.
An IC label can be used as a label for in-mold forming that comprises a thermoplastic resin film and is bonded to a resin molding by in-mold forming, so as to take advantage of that property of an IC module by which it is capable of repeated data sending/receiving. A resin molding obtained as a molded article including the label united therewith is usable in both indoor and outdoor applications and even in water, and can be used advantageously even in severe environments as containers for frozen foods, industrial products, and various containers for chemicals, in manufacturing process control applications and physical distribution management applications, and as tote boxes, etc. This labeled resin molding is effective in preventing frauds, such as disguise and alteration, from being committed through label replacement.
Patent document 6 proposes an extrusion-molded resin article obtained by setting an IC module as it is in a predetermined position in a mold and extruding a thermally molten resin into the mold to embed the IC module therein. When an IC module is used in such product production processes in which it is embedded in a resin molding, the IC module undergoes a heating step. It has been said that IC modules have heat resistance sufficient to enable the modules to withstand temperatures necessary for molding in producing thermoplastic resin moldings. These IC modules are highly bulky so as to protect the circuit and are expensive.
However, small IC modulus developed recently need not employ a highly heat-resistant polyimide film as the constituent base film because there is no need of heating to a high temperature in IC chip/antenna bonding. Partly for the purpose of reducing the cost of IC modules themselves, inexpensive polyester films and polyethylene films have come to be used. Furthermore, there is a fear that the trend toward size reduction in IC chips themselves may lead to a decrease in resistance to thermal stress due to the decrease in heat capacity. It is presumed that even a process for producing the same extrusion-molded resin article will pose problems such as a deteriorated product yield in the future if the heat history for the IC modules is not sufficiently taken into account.
Patent document 7 includes a statement concerning a non-contact data carrier label usable in in-mold forming. However, in patent document 7 also, the label is used in a manner in which the IC module comes into direct contact with a thermally molten resin during in-mold forming. This technique hence causes troubles, for example, that the IC module breaks due to an abrupt temperature change as in the case of the IC modules described above and that the antenna part deforms due to the pressure applied for extruding the molten resin. This prior-art label is insufficient from the standpoint of IC module protection in the technique of in-mold forming.
IC chips have extremely low resistance to electrostatic charge, and there may be a possibility that the IC chips might break due to static buildup in the label material during label formation, printing, or in-mold forming. Because of this, to take a measure against static buildup is important.
Patent Document 1: JP-A-11-134460
Patent Document 2: JP-A-11-231782
Patent Document 3: JP-A-2002-074303
Patent Document 4: JP-A-02-084319
Patent Document 5: JP-A-09-207166
Patent Document 6: JP-A-08-056799
Patent Document 7: JP-A-2002-049905